Enhanced Phase Stability and Photoluminescence of Eu3+ Modified t-ZrO2 Nanoparticles

Tetragonal ( t ) ZrO₂ nanoparticles have been obtained by a partial Eu³⁺→Zr⁴⁺ substitution, synthesized using a simple oxalate method at a moderate temperature of 650°C in air. The Eu³⁺ additive, 2 mol% used according to the optimal photoluminescence (PL), gives small crystallites of the sample. On raising the temperature further, the average crystallite size D grows slowly from 16 nm to a value as big as 49 nm at 1200°C. The Eu³⁺: t -ZrO₂ nanoparticles have a wide PL spectrum at room temperature in the visible to near-IR regions (550–730 nm) in the ⁵D₀→⁷F_J (Eu³⁺), J =1–4, electronic transitions. The intensity of the ⁵D₀→⁷F₄ group is as large as that of the characteristic ⁵D₀→⁷F₂ group of the spectrum in the forced electric-dipole allowed transitions. The enhanced t -ZrO₂ phase stability and wide PL can be attributed to the combined effects of an amorphous Eu³⁺-rich surface and part of the Eu³⁺ doping of ZrO₂ of small crystallites.     

Methicillin-resistant Staphylococcus aureus: a four-year experience in a spinal cord injury unit in Spain

Methicillin-Resistant Staphylococcus aureus (MRSA) infection poses a problem for both acute and long-term-care facilities, Spinal Cord Injury units included. This paper describes the 4-year evolution of MRSA outbreaks in a SCI unit in a university hospital where control measures were implemented from the first case detected. The protocol procedure was as follows: contact isolation, washing with antiseptic soap both those infected and those sharing the same room, contacts study and monitoring of MRSA patients up to the time when three consecutive negative cultures (sampled at time lapses of over 48 h) were obtained, antiseptic soap for the health-care personnel to wash their hands, and cultures of the nares done on the personnel in the event of an outbreak. Twenty-one (3.4%) MRSA positive cases were detected out of 550 admissions registered during the study period (November 1990 through October 1994). The evolution occurred in three outbreaks and six isolated MRSA positive patients without secondary cases. 71.5% of the cases were nosocomial. Seven (33%) were colonizated and 14 (67%) infected. The 14 patients infected presented 15 infections: nine with urinary tract infections, three surgical wound infections, two tracheostomy wound infections, and one patient with a decubitus ulcer infection. Two of those with urinary tract infections presented with secondary sepsis. No carriers were detected amongst the personnel. Urinary tract colonizations responded to treatment with cotrimoxazol except in two cases in which combined treatment was required (cotrimoxazol plus rifampicin). The patients with a MRSA positive tracheal aspirate were negative after combined treatment. Wounds and cultures of the nares responded favorably to initial treatment. One of the patients with a urinary tract infection and sepsis died the infection being a contributing cause. The prospective follow-up of the patients with MRSA positive cultures and the precocious implementation of isolation measures allow for the limitation of transmission, even although complete eradication is not possible.     

Study of the reduction of UO2 by magnesium or calcium dissolved in molten chlorides

The reduction of solid UO₂ to uranium by magnesium or calcium dissolved in their molten chlorides has been studied. The rate of reduction per unit area of UO₂ surface, at constant temperature and concentration of reductant in the molten chloride, was found to increase with time to a constant value. The rate of reduction per unit area was observed to be proportional to the concentration of reductant in the molten salt. The small increase observed in the reaction rate over the temperature range 750° to 850°C, suggests that the reduction is controlled by transport of the reductant to the reaction site. Solidified salt, containing UO₂ pellets which had been partially reduced, was sectioned, polished, and examined microscopically. The products of the reduction reaction form concentric layers around the UO₂ pellets. Layers of metallic uranium and oxide containing small amounts of dispersed salt alternated with layers of salt containing small amounts of metallic uranium and oxide. The layers ruptured, presumably because the volume of the products, uranium and oxide, is greater than the volume of the UO₂. Therefore, an impervious layer did not form on the oxide surface to inhibit the reduction reaction.     

Nutritional and antioxidant status of an institutionalized elderly group in Murcia (Spain)

The aging of the population is giving rise to a large number of studies aimed at improving the quality of life, considering diet as a major contributing factor in this life stage. The objectives of the present study were to evaluate the nutritional status of a group of institutionalized elderly in Murcia, Spain, and to relate the diet to anthropometric and biochemical indices, paying special attention to total antioxidant status. The dietary evaluation showed excessive intakes of proteins and lipids, and deficiencies in those of carbohydrates, dietary fiber, zinc, iodine and vitamins A, E and D. The high proportion of overweight observed were not significantly correlated to the energy intakes. Although total plasma antioxidant status was low (0.62 mM eq Trolox and 0.98 mM eq Fe(II)) compared with reference values, estimated oxidative risk in this group of elderly was low according to plasma levels of vitamins C, A & E.     

On the graphical analysis of the electronic structure of ferromagnetic clusters of medium size

In a previous work, a theoretical approach, suitable to describe systems having a large number of fermions, was proposed, and results for ferromagnetic surface clusters of medium size (100-1000 atoms) were presented. The aim of the present contribution is to complete this previous work. Several significant theoretical and technical details, omitted previously, are provided here. The obtained spin orbitals are analyzed, by studying their symmetry, energy, and d contribution properties.     

Analog Adaptive Median Filters

The implementation of analog adaptive median filters for image processing is discussed. The adaptive median filter is based on transconductance comparators, whose saturation current is adapted to act as a local weight operator. Transistor level simulations have shown excellent results in removing incidence noise. A 249 × 209 pixel image, corrupted with 35% salt and pepper noise, is used to test the adaptive median filter. All the simulations were made using BSIM3's level 49 model and 1.2 m MOSIS technology parameters.     

Synthesis and characterization of Cu nanotubes and nanothreads by electrical arc evaporation

We report the formation and characterization of copper nanostructures, nanotubules and nanothreads, which were obtained by electrical arc evaporation of Cu electrodes under varied conditions of He ambience. Electrical arc evaporation was done with approximately 10 V and (approximately 50-100 A) DC current. The current was used in a pulse mode. The evaporated material was condensed on a formvar-coated Cu grid mounted on a liquid N2-cooled specimen holder. Transmission electron microscopy was employed to characterize the condensed materials. These investigations revealed that the condensed materials consisted of the mentioned nanostructures. Nanotubes and nanothreads are formed for a He pressure in the chamber corresponding to approximately 140 and approximately 500 torr, respectively. Extensive electron microscopic investigations showed that the diameter of the nanotubes varied from approximately 5 nm to approximately 50 nm and their length from 2 microns to 3 microns.     

DRYING CHARACTERISTICS OF TAPIOKA

Experimcntal studies were carried out on a multipurposc industrial solar drycr having corrugated absorber with two glass covers. Drying charactcristics of Tapioka wcre obtained on the fixed bed portion of this dryer     

The electronic structure of oxide-supported tungsten oxide catalysts as studied by UV spectroscopy

The UV spectra of tungsten oxide catalysts supported on alumina, titania and zirconia, and on titania–alumina and titania–zirconia mixed oxides are reported and discussed. Evidence is provided for the different electronic structure of supports and catalysts, which could affect the behavior of the tungsten oxide centres in the different cases. On alumina, tungsten oxide centres are “isolated” by the insulating support, while on titania-based materials they are likely in electronic contact with each other and with Ti centres through the support conduction band. In the case of WOx2013;ZrO₂, the 5d levels of tungsten ions fall just below of the lower energy limit of the support conduction band. This revised version was published online in July 2006 with corrections to the Cover Date.